The present invention relates to an optical waveguide device. More particularly, the invention relates to a prism coupling device which is used as an optical coupling means arranged in an optical system comprising optical elements such as an optical integrated circuit, an optical sensor and other optical devices.
As a conventional optical waveguide means for guiding light through a prism into an optical waveguide layer, it is known to use an arrangement in which a prism is pressingly bonded directly on a surface of the optical waveguide layer, so as to easily obtain a waveguide structure having a high coupling efficiency. However, with the conventional structure, the waveguide means is easily influenced from mechanical vibrations and shocks, which changes the coupling efficiency thereof. In order to obviate such a problem, it has been proposed an arrangement in which a gap adjusting layer having a low index of refraction is disposed between a cementing layer having a high index of refraction for bonding the prism and an optical waveguide layer having a high refractive index, so as to keep the gap length between the prism and the optical waveguide constantly unchanged.
However, the above-mentioned prior art arrangement involves a problem of misalignment of light, that is, the light is guided to a wrong point of the waveguide when the light is optically treated, such as when the light is to be condensed or reflected, when the light penetrates an optical element and/or when the light is coupled after guided into the high refractive index waveguide layer, thus degrading the optical characteristic thereof.